1. Field of the invention
This invention relates to a disc apparatus and thread-moving method therefor, and more particularly to a thread-moving method for causing an optical pickup to access at a high speed to a target position, and disc apparatus utilizing the same.
2. Description of the prior art
In a conventional disc apparatus of this kind, the tracks to be jumped over is calculated in number depending upon a current-position address and a target-position address. Based on the calculated number, a number for acceleration or deceleration is calculated according to a table or calculating equation, thereby accelerating or decelerating a thread motor.
In the prior art, however, the acceleration and deceleration of the thread motor are carried out while monitoring the number of tracks. Accordingly, data reading (track-on) is commenced in a state that the thread (pickup) moving speed has not been decelerated to a sufficiently reduced extent, resulting in a problem of irregularity in tracking.
On the other hand, conventionally a constant level voltage is continuously applied to the thread motor. This might accelerate the pickup unlimitedly, possibly raising a problem of difficulty in controlling the rotation of the thread motor. Thus, there has been a difficulty for pickup to get access to a desired position in a brief period of time.